Not sure if it's a hard drive issue. Went to restore a file from Time Machine. Hit Cancel because it was taking a long time to access. The screen went all gray. After a few minutes, I did a hard reboot. I heard the power up tone, but all I see are vertical gray lines on the monitor. I've tried to reset the PRAM, it won't go that far, I don't think it sees the keyboard. Thinking the hard drive went bad, as I don't hear it making noise. I've disconnected everything, opened the side and used compressed air to blow out all the dust. Nothing works. Opinions?